1. Field of the Invention
The present invention provides a cooled optical light guide suitable for placement between a scintillator array and an array detector. A method of temperature stabilization for photomultiplier based detectors is disclosed.
2. Description of the Background Art
The main drawback of silicon-based photomultiplier (SiPM) devices is variation of detector performance with even small temperature fluctuations.
Rapid development in the field of silicon photomultipliers (SiPM) solidified their position as replacements for standard vacuum photomultiplier tubes (PMTs). Silicon-based devices possess equally high amplification gain, but hold strong advantage in compactness, insensitivity to magnetic fields, lower bias voltages and potentially lower costs, making them a viable alternative to PMT technology [1-5]. Certain limitations still prevent SiPMs from completely replacing vacuum PMTs. One of the limitations of the newly developed silicon photomultiplier technology is low signal-to-noise ratio (SNR) compared to the well-established vacuum photomultipliers. Lower SNR results in poorer energy resolution and fluctuations in the center of gravity (COG) calculations of the position of the scintillation event in the light sharing systems, which results in errors in event localization. It has been shown by multiple research groups [6-8] that SNR in SiPMs improves substantially with lowering the temperature of the light sensor. In addition, gain of SiPMs depends on the sensor temperature, in some cases quite dramatically [9,10]. While bias voltage adjustment mitigates the issue of drifting amplification gain, it does not address an increase in noise with increased temperature. Medical imaging applications, positron emission tomography (PET) and single photoemission computed tomography (SPECT), for example, can benefit greatly from improved signal-to-noise ratio, due to limited light yield of scintillation materials. It is therefore highly advantageous to lower and stabilize the SiPM sensors temperature in order to improve the operation of the SiPM-based detection modules.
Thermoelectrically cooled single module SiPM devices are being offered by commercial vendors, while the cooling of multi-pixel arrays of SiPMs is an active area of research. Several cooling methods are being considered and implemented. The main challenge is to deliver the cooling power as close as possible to the SiPM arrays and in uniform and stable manner. Piped distributed cooling liquids or gas, or blowing cool air present their own technical challenges with the uncertain outcomes as to the uniformity and efficiency of delivery of the cooling power.